Metallized laminated structure and method of making a plastic article

ABSTRACT

A metallized laminated structure suitable for making a rigid container having a metallic appearance is provided. The laminated structure includes a metallized film and a thermoplastic sheet. At least a portion of the thermoplastic sheet is bonded to the metallized film through a lamination process. The metallized film includes a metallic layer, a sealable layer, and a polypropylene core between the metallic layer and the sealable layer. The thermoplastic sheet includes at least one layer of a polypropylene or a thermoplastic olefin. Or the thermoplastic sheet includes at least one layer of a polypropylene and at least one layer of a thermoplastic olefin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/566,513, filed Dec. 4, 2006, U.S. Pat. No. 7,763,361currently pending, the entire disclosure of which is hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to thermoforming and moreparticularly to a laminate that is thermoformable, and to articles madefrom the thermoformed laminate.

It is often desirable to provide a metallic appearance to plasticarticles, such as, but not limited to, rigid plastic food containers.One approach to achieving this objective is to make the container from apolymer that contains a metallic pigment. However, pigment is relativelyexpensive especially in use with disposable food containers. Anotherapproach is to paint the container with a metallic paint. However, paintcan chip or flake.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses the above problem by providing ametallized laminated structure suitable for making a rigid containerhaving a metallic appearance. The laminated structure includes ametallized film and a thermoplastic sheet. At least a portion of themetallized film is bonded to the thermoplastic sheet. The metallizedfilm includes a metallic layer, a sealable layer, and a polypropylenecore between the metallic layer and the sealable layer. Thethermoplastic sheet includes at least one layer of a polypropyleneand/or at least one layer of a thermoplastic olefin.

For example, the thermoplastic sheet may include one polypropylene layerbetween two thermoplastic olefin layers. The polypropylene layer mayhave a melt index of about 2.0 and each thermoplastic olefin layer mayhave a melt index of about 2.0 and a shore hardness of about D40. Thethermoplastic sheet may have a thickness of around 40 mils to around 60mils.

The metallic layer of the film may include a polyolefin-base resin and avacuum-deposited metal coating, such as aluminum. The metallized filmmay have a thickness of about 1.5 mils.

Another aspect of the present invention is a method for making a plasticarticle with the metallized laminated structure. The method includesextruding the layer or layers of the thermoplastic material into thethermoplastic sheet and then laminating the metallized film to thethermoplastic sheet at a predetermined lamination temperature. Afterlaminating the metallized film and the thermoplastic sheet into ametallized laminated structure, the structure may be thermoformed orshaped into an article, such as the body of a food container.

The lamination temperature may vary from about 300° F. to about 335° F.The step of laminating the metallized film to the thermoplastic sheetmay include feeding the thermoplastic sheet and the metallized filmthrough a roll laminator.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a side view of a metallized laminated structure according toan embodiment of the present invention;

FIG. 2 is a side view of a metalized laminated structure according toanother embodiment of the present invention;

FIG. 3 is a plan view illustrating a lamination process according to anembodiment of the present invention; and

FIG. 4 is a perspective view of a container formed from the metallizedlaminated structure of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings in which some but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

The present invention provides a laminated structure 10 suitable forthermoforming. The laminated structure 10 includes a metallized film 12and a thermoplastic sheet 14.

The thermoplastic sheet 14 includes one or more layers of apolypropylene. For example, according to one embodiment of the presentinvention and as illustrated in FIG. 1, the thermoplastic sheet 14includes one polypropylene layer 16. The polypropylene layer 16 includesa first side 30 and a second side 32. Together, the sides 30, 32 definea thickness of the layer 16. The polypropylene layer 16 is formedthrough an extrusion process.

The thermoplastic sheet may include one or more layers of athermoplastic olefin in addition to or instead of the one or morepolypropylene layers. A thermoplastic olefin may be prepared by meltblending polypropylene with an EPDM, a SBS or a SEBS block copolymer orcopolymers along with various additives known in the art. For example,the one layer 16 in the FIG. 1 embodiment may be a layer ofthermoplastic olefin instead of polypropylene. For another example andas shown in the FIG. 2 embodiment, the thermoplastic sheet includesthree layers 16, 18, 19. The first and third layers 18, 19 are of athermoplastic olefin and the second layer 16 is of a polypropylene. Theone layer of the polypropylene 16 is between the two layers of thethermoplastic olefin 18, 19. Each layer includes first and second sidesthat define a thickness of the layer. Together the layers define thethickness of the thermoplastic sheet. The multi-layer thermoplasticsheet is formed through a co-extrusion process.

The metallized film 12 includes at least one metallic layer. Themetallic layer may include a polyolefin-base resin and a metal coating.A surface of the polyolefin-base resin may be subject to a dischargetreatment for promoting adhesion with the metal coating. The metalcoating may be applied by a known metallizing method such as a vacuumevaporation method, a sputtering method, or a chemical vapordecomposition method. The metal coating may vary. For example, the metalin the coating could be Ag, Al, Au, Co, Cr, Fe, Ni, Zn, or variousalloys.

The metallized film 12 may further include a polymer core and a sealablelayer. For example, according to the embodiments illustrated in FIGS. 1and 2 the metallized film 12 includes a polypropylene core 20, ametallic layer 26, and a sealable layer 28. The polypropylene core 20includes a first side 22 and a second side 24. The metallic layer 26 isadjacent to the first side 22 of the polypropylene core and the sealablelayer 28 is adjacent to the second side 24 of the polypropylene core.Both the metallized layer and the sealable layer define surfacesopposite the polypropylene core that together define a thickness of themetallized film.

Metallized films are commercially available. For example, the metallizedfilm described above for the illustrated embodiments is availablethrough the VIFAN division of the VIBAC Group.

The laminate structure is formed by bonding at least a portion of themetallized film to at least a portion of the thermoplastic sheet. Thethermoplastic sheet and the metallized film may be bonded togetherthrough a lamination process as illustrated in FIG. 3. In general, thethermoplastic sheet and the metallized film are fed through a pair ofnip rollers 40 or similar device at a predetermined laminationtemperature. The temperature and the pressure from the rollers create abond between the thermoplastic sheet and the metallized film, or morespecifically between the thermoplastic sheet and the sealable layer ofthe metallized film, or between the thermoplastic sheet and the metalliclayer of the metallized film. The lamination process may occur in-linewith the extrusion machine 35 that forms the thermoplastic sheet, asshown in FIG. 3. For example, the nip region of the polishing roll in aconventional extrusion process may be used as a lamination roll to bondthe thermoplastic sheet and the metallized film together. Alternatively,the bonding of the thermoplastic sheet and the metallized film may bedone off-line from the extrusion process.

The lamination temperature, the thicknesses of the metallized film andof the thermoplastic sheet and the characteristics of the materials ofthe metallized film and the thermoplastic sheet contribute to the bondstrength between the metallized film and the thermoplastic sheet.

For example, in one embodiment, the thermoplastic sheet has a thicknessof about 40 mils and includes two thermoplastic olefin layers and onepolypropylene layer between the two thermoplastic olefin layers{TPO/PP/TPO}. Each thermoplastic olefin layer has a thickness of about 5mils and shore hardness of about D40. The polypropylene is a copolymerhaving a melt index of 2.0, as per ASTM D1238. The metallized film is aCXM grade film from VIFAN that has a thickness of about 1.5 milthickness and includes a polypropylene core between a sealable layer anda metallic layer with vacuum deposited aluminum. The thermoplastic sheetand the metallized film may be bonded together at a laminationtemperature of about 300° F.

In another embodiment, the thermoplastic sheet has a thickness of about60 mils and includes one polypropylene layer. The polypropylene is acopolymer having a melt index of 2.0. The metallized film is a CXM gradefilm from VIFAN that has a thickness of about 1.5 mil thickness andincludes a polypropylene core between a sealable layer and a metalliclayer with vacuum deposited aluminum. The thermoplastic sheet and themetallized film may be bonded together at lamination temperatures fromabout 300° F. to about 335° F.

Although the embodiments above generally describe a metallized filmhaving a sealable layer, in other embodiments of the present inventionthe metallized film may not have a separate sealable layer. As disclosedabove, the thermoplastic sheet may be bonded directly to the metalliclayer of the metallized film. In other embodiments, the thermoplasticsheet may be bonded directly to the polypropylene core without aseparate sealable layer. Also, a separate adhesive, such as a pressuresensitive adhesive, may be employed to facilitate the bonding of thethermoplastic sheet to either the polypropylene core or metallic layerof the metallized film.

The bond between the metallized film and the thermoplastic sheet of thelaminate structure is strong enough to withstand additional shapingprocesses. For example and as shown in FIG. 4, the laminated structuremay be shaped into a container 50 through a thermoforming process. Thethermoformed container 50 has a mirror-like polish appearance from themetallized film and rigidity from the thermoplastic sheet. One in theart should appreciate that additional functional layers may be added tothe thermoplastic sheet to achieve greater rigidity or greater barrierproperties. Other layers may include known barrier materials such asethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), or nylon.Also, modifiers or additives, such as clarifying agents or oxygenscavengers, may be blended or added to one or more of the layers forimproving the gas barrier properties of the container or color masterbatch to provide varying degree of visual effect.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A laminated structure for a thermoformed article, the structurecomprising: a metallized film including a polypropylene core have afirst side and a second side, a metallic layer adjacent the first side,and a sealable layer adjacent the second side; and a thermoplastic sheetincluding at least one layer of a polypropylene and two layers of athermoplastic olefin, wherein one layer of the polypropylene is disposedbetween the two layers of the thermoplastic olefin, and wherein at leasta portion of the metallized film is bonded to the thermoplastic sheet.2. The laminated structure according to claim 1, wherein at least aportion of the sealable layer is bonded to the thermoplastic sheet. 3.The laminated structure according to claim 1, wherein at least a portionof the metallic layer is bonded to the thermoplastic sheet.
 4. Thelaminated structure according to claim 1, wherein the thermoplasticolefin has a melt index of about 2.0 and a shore hardness of about D40and the polypropylene has a melt index of about 2.0.
 5. The laminatedstructure according to claim 4, wherein the thermoplastic sheet has athickness around 40 mils to around 60 mils and the metallized films hasa thickness of about 1.5 mils.
 6. The laminated structure according toclaim 1, wherein the metallic layer includes a polyolefin-base resin anda vacuum-deposited metal coating.
 7. The laminated structure accordingto claim 6, wherein the metal coating is aluminum.
 8. A method of makinga plastic article, comprising the steps of: extruding a thermoplasticsheet comprising at least one layer of polypropylene and two layers of athermoplastic olefin, wherein the at least one layer of polypropylene isdisposed between the two layers of the thermoplastic olefin; laminatinga metallized film to the thermoplastic sheet at a predeterminedtemperature; and thermoforming the laminated thermoplastic sheet and themetallized film into a predetermined shape, wherein the thermoplasticolefin has a melt index of about 2.0 and a shore hardness of about D40and the polypropylene has a melt index of about 2.0.
 9. The methodaccording to claim 8, wherein a thickness of the thermoplastic sheet isabout 40 mils and a thickness of the metallized film is about 1.5 milsand the predetermined temperature during the lamination step is about300° F.
 10. The method according to claim 8, wherein the thermoplasticsheet has one layer of a polypropylene copolymer having a thickness ofabout 60 mils and a melt index of about 2.0 and the metallized film hasa thickness of about 1.5 mils and the predetermined temperature duringthe lamination step is around 300° F. to around 335° F.
 11. The methodaccording to claim 8, wherein the step of laminating includes feedingthe thermoplastic sheet and the metallized film through a rolllaminator.
 12. The method according to claim 8, further includes forminga metallized film by vacuum depositing a metal coating onto apolyolefin-base resin.
 13. The method according to claim 8, wherein thelamination of the metallized film to the thermoplastic sheet occursin-line with the extrusion of the thermoplastic sheet.
 14. The methodaccording to claim 8, wherein the metallized film includes a sealablelayer for bonding with the thermoplastic sheet.
 15. The method accordingto claim 8, wherein an adhesive is applied to either the metallized filmor the thermoplastic sheet for bonding between the metallized film andthe thermoplastic sheet.